JPH10237420A - Anaerobically curable sealant composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an anaerobically curable sealant compsn. which has a high flexibility even after subjected to heat hysteresis by compounding a urethane (meth)acrylate prepolymer, a free-radical-polymerizable monomer, an org. peroxide, and fine core-shell particles. SOLUTION: This compsn. comprises a urethane (meth)acrylate prepolymer having a urethane main chain and terminal (meth)acryloyloxy groups, a free- radical-polymerizable monomer [e.g. ethyl (meth)acrylate], an org. peroxide (e.g. cumene hydroperoxide), and 0.1-80wt.% (based on the compsn.) fine core- shell particles. The compsn. may further contain a cure accelerator, a filler, a plasticizer, a tackifier, etc., if necessary. The particles are produced by polymerizing a polymerizable monomer for cores to form cores comprising a rubberlike polymer having a glass transition point lower than the ambient temp. and then polymerizing a polymerizable monomer for shells to form shells comprising a glassy polymer having a glass transition point higher than the ambient temp.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anaerobic hardening type liquid gasket composition for forming a seal between two surfaces of a flange having a large displacement, and preferably to a lubricating oil for industrial use, an internal combustion engine, a drive unit and the like. The present invention relates to an anaerobic curable liquid gasket composition effective for preventing leakage of water.

[0002]

2. Description of the Related Art Conventionally, in a place where sealing is required in the fields of automobile parts, electric parts, various mechanical parts, etc., as a method of connecting and sealing parts by an assembly line, a molded gasket is interposed on a sealing surface. A method of pressure contact and a method of sealing by interposing a liquid gasket on a sealing surface have been adopted. Of these methods, a method of sealing by interposing a liquid gasket between the sealing surfaces is described in the field: a gasket in-situ molding method in which a liquid sealing agent is automatically applied by a robot or the like on an assembly line and sealed.
rmed In Place Gaskets) has become mainstream because of its high productivity, low cost, and reliable sealing performance. Room temperature curing type silicone material (silicone RTV) that cures by reacting with moisture in the atmosphere as a FIPG material, and cuts off oxygen by sandwiching a sealant on the flange surface and cures in a short time by contacting the metal surface Anaerobic gaskets containing urethane (meth) acrylate as a main component are mainly used. Among them, silicone RTVs are currently most used because of their good heat resistance, good workability and good compatibility with the painted flange surface.

However, in the case of FIPGs using silicone RTVs, in recent years, as oils such as engine oils have been improved in performance, oils have given greater damage to silicone rubber, and oil resistance has become a problem.

In particular, acrylic anaerobic-curing sealants are increasingly used for oils and the like used in automobiles and the like. Since this sealant is acrylic, it has a drawback that the sealant is more flexible than the silicone composition. What is needed as a sealant is a repulsive force sufficient to maintain flexibility and sealing properties that can cope with vibration and stress of a sealing portion such as a flange. For these reasons, acrylic anaerobic-curing sealants have been insufficient for practical use, and silicone RTV has been mostly used.

[0005] Also, since the flange material of an oil pan or the like is often formed by joining different materials such as iron and aluminum, a large lateral direction is applied to the flange surface due to a difference in thermal expansion coefficient due to a temperature change in an engine part. Shift occurs,
It is required that the sealing agent layer has high followability. This problem is particularly significant for larger engines. The lateral displacement of the flange surface can be mitigated by increasing the thickness of the gasket, but increasing the thickness of the gasket causes a fatal disadvantage that anaerobic hardening does not occur.

Therefore, a technique for imparting flexibility to an anaerobic curable polymerizable composition which is an acrylic composition has been considered. These techniques include urethane acrylate or a high molecular weight prepolymer in which the main chain is obtained by polymerizing a soft segment such as polyether as an acrylic raw material.The composition itself is made flexible by adding a plasticizer to the acrylic polymerizable compound. A technique of adding flexibility or adding synthetic rubber particles such as acrylic rubber and butyl rubber to give flexibility to the entire composition has been used.

[0007]

However, when a high molecular weight prepolymer containing a soft segment is used, the temperature of 120 ° C.
When used under a moderate atmosphere, that is, when subjected to a thermal history, the flexibility is reduced. In other words, the flexibility of the sealing material is lost with time in a portion where the temperature becomes high. Further, the type to which the synthetic rubber particles are added retains flexibility, but has extremely poor solubility at the time of production, requiring a long time for the production process. Furthermore, if the sealant is stored in a liquid state, the rubber particles may settle or agglomerate and become clogged by the nozzle of the coating machine. Further, when a plasticizer is used, there is a disadvantage that the plasticizer permeates from the cured sealant.

Further, in the conventional anaerobic hardening type liquid gasket, when engine oil, auto transmission fluid, gear oil and the like are adhered to the surface on which the sealant is applied, that is, the adhesive surface, the adhesive force is significantly reduced. Usually, a release agent or a polishing oil adheres to the bonding surface, and degreasing and cleaning with an organic solvent or a cleaning agent is required.

Further, an anaerobic curable composition is applied to a sealing surface such as a flange in an appropriate amount, and when the sealing surface is tightened, a portion where oxygen is blocked is polymerized and cured to form a sealing material, but the amount of application cannot be strictly controlled. In some cases or when an excessive amount is applied for reliable sealing performance, it may protrude from the flange surface. Since the portion of the anaerobic curable composition that protrudes and is in contact with the air is not cured, it is necessary that the anaerobic curable composition does not adversely affect the substance that attempts to prevent leakage.

In particular, when an anaerobic curable composition is used for engines such as automobiles and missions, it is necessary that the uncured anaerobic curable composition protruding from the joint surface of the flange portion is uniformly dispersed in each oil. Had become a condition. Anaerobic curable compositions to which synthetic rubber particles are added as a softening agent have a problem that they lack dispersibility.

[0011]

The present invention relates to an anaerobic curable composition, and more particularly to an anaerobic curable composition having excellent flexibility even after being subjected to a heat history. That is, the present invention provides an anaerobic curable sealant comprising a urethane (meth) acrylate prepolymer, a radical polymerizable monomer and an organic peroxide, and further comprising core-shell fine particles comprising a rubbery polymer core and a glassy polymer shell. An anaerobic curable sealant composition characterized by the following:

The urethane (meth) acrylate prepolymer used in the present invention is a prepolymer having a urethane structure in the main chain and having (meth) acryloyloxy at the terminal. This is obtained by reacting a compound having two or more functional hydroxyl groups with a compound having two or more functional isocyanate groups to synthesize a polyurethane prepolymer and introducing a (meth) acryloyloxy group into a molecular terminal thereof. For example, a polyurethane prepolymer obtained by mixing and reacting a polyether polyol and an organic diisocyanate at a molar ratio of 1: 1 to 1: 2 in a diluting solvent reacts with all remaining isocyanate groups of the polyurethane prepolymer. Obtained by reaction with a (meth) acrylate monomer having a sufficient amount of activated hydrogen.
The urethane (meth) acrylate may be used singly or as a mixture of two or more kinds.

The molecular weight of the urethane (meth) acrylate prepolymer is such that two hydroxyl groups such as polyether polyol are used.
It is possible to freely select the molecular weight of the prepolymer obtained by selecting the molecular weight of the compound having more than one functionality or controlling the degree of reaction between the compound having two or more hydroxyl groups and the compound having two or more isocyanate groups. .

Compounds having two or more hydroxyl groups include ethylene glycol, 1,2-propylene glycol,
1,3-butanediol, 1,4-butanediol, diethylene glycol, triethylene glycol, 1,6
-Hexanediol, neopentyl glycol, trimethylolmethane, trimethylolpropane, glycerin, pentaerythritol, 1,2,6-hexanetriol, bisphenol A hydroxide, polyether polyol, polyester polyol and the like.

Examples of the compound having two or more isocyanate groups include diphenylmethane diisocyanate, tolylene diisocyanate, naphthalene diisocyanate, xylene diisocyanate, and hexamethylene diisocyanate.

The (meth) acrylate having active hydrogen includes hydroxylalkyl (meth) acrylate, aminoalkyl (meth) acrylate and phenylalkyl (meth) acrylate.

The radical polymerizable monomers of the present invention include ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, and n-hexyl ( (Meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate,
n-lauryl (meth) acrylate, 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth)
Acrylate, 2-phenoxyethyl (meth) acrylate, stearyl (meth) acrylate, tridecyl (meth) acrylate, 3-methoxypropyl (meth)
Examples include acrylate, 3,3-methoxymethylpropyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, and hydroxypropyl (meth) acrylate. These radical polymerizable monomers are 1
They may be used alone or as a mixture of two arbitrary types.

The core-shell fine particles used in the present invention are granular fine particles whose core is a rubber-like polymer and whose shell is a glass-like polymer. The core-shell structured particles have "elasticity" in the core portion and "hardness" in the shell portion, and do not dissolve in the liquid resin. The polymer forming the "core" has a glass transition temperature substantially below ambient temperature. The polymer that forms the "shell" is
It has a glass transition temperature substantially above ambient temperature. Ambient temperature is defined as the temperature range in which the sealant is used.

In the production of the preferred powder particles used in the present invention, the production is carried out by first polymerizing a polymerizable monomer as a core portion. Examples of the polymerizable monomer include (meth) acrylate monomers such as n-propyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and n-decyl (meth) acrylate, styrene, and vinyl. Aromatic vinyl compounds such as toluene and α-methylstyrene; vinyl cyanide compounds such as acrylonitrile and methacrylonitrile; vinylidene cyanide; 2-hydroxyethyl (meth) acrylate; 3-hydroxybutyl (meth) acrylate; Hydroxyethyl fumarate, hydroxybutyl vinyl ether, monobutyl maleate, butoxyethyl methacrylate and the like. Further, ethylene glycol di (meth) acrylate, butylene glycol di (meth) acrylate, tributyl Reaction of tyrolpropane di (meth) acrylate trimethylolpropane tri (meth) acrylate, hexanediol di (meth) acrylate, hexanediol tri (meth) acrylate, oligoethylene di (meth) acrylate, oligoethylene tri (meth) acrylate Examples thereof include a crosslinkable monomer having two or more functional groups, an aromatic divinyl monomer such as divinylbenzene, triallyl trimellitate, triallyl isocyanate, and the like. One or more of these can be selected and used.

The rubber properties change depending on the molecular weight, molecular shape and crosslink density of the polymer obtained by polymerizing the above polymerizable monomers. In the present invention, the core must be a rubbery polymer at room temperature. More preferably, the obtained polymer has a glass transition point of -10 ° C or lower.

Next, a second polymerization in which the thus obtained polymer particles are used as a core and a polymerizable monomer is further polymerized to form a shell made of a polymer having a glassy property at room temperature is performed. Do. As the polymerizable monomer used at this time, the same polymerizable monomer as that used for obtaining the core can be selected and used. However, in the present invention, the shell portion must be a glassy polymer at room temperature. Preferably, the glass transition point of the obtained polymer is preferably 70 degrees or more. This can be determined by the molecular weight, molecular shape, crosslink density, etc. of the polymer obtained when the selected polymerizable monomer is copolymerized. If it is not glassy at room temperature,
When the present polymer particles are mixed into a liquid resin capable of radical polymerization to form a sealant composition, the particles are swollen by the radical polymerizable monomer, and the viscosity increases with time during storage, and the It will be. That is, the storage stability becomes insufficient.

Preferred examples of the polymerizable monomer used as the shell material include (meth) acrylates having an alkyl group having 1 to 4 carbon atoms, such as ethyl (meth) acrylate, n-butyl acrylate, methyl methacrylate, and butyl methacrylate. Is mentioned. These may be used alone or in combination of two or more. Among them, methyl methacrylate is particularly preferable.

The amount of the core-shell fine particles added to the total composition is as follows:
0.1 to 80% by weight, preferably 5 to 65% by weight
Is the amount of If it is less than 5% by weight, it is difficult to impart excellent flexibility to the cured product, and if it is 80% by weight or more, the viscosity becomes extremely high, and the storage stability decreases. A more preferable addition amount is 10 to 40% by weight.

Anaerobic is a property that dislikes air, that is, a property in which a stable and liquid state is maintained in the presence of air or oxygen, but polymerization is started immediately when air or oxygen is excluded. Anaerobic sealant has been used for bonding metal parts
It is used for sealing, preventing loosening, fixing a fitting portion, and the like, and is known. It is known that an anaerobic curable composition comprises a radical polymerizable monomer such as (meth) acrylate or a prepolymer thereof, and a polymerization initiator such as an organic peroxide, a curing accelerator, a polymerization inhibitor, and the like. .

Specific examples of the organic peroxide include cumene hydroperoxide, t-butyl hydroperoxide, diisopropylbenzene hydroperoxide,
In addition to hydroperoxides, there are diacyl peroxides, dialkyl peroxides, ketone peroxides, peroxyesters, and the like. Cumene hydroperoxide is particularly preferred in terms of stability and curing rate.

For effective anaerobic curing, it is preferable to add a curing accelerator in addition to the organic peroxide. Examples of the curing accelerator include organic sulfonimides, amines, and organic metal salts. Among them, the organic sulfonimide is preferably o-benzoixulfimide, and the amines are diethylamine, triethylamine, N, N-amine. Dimethyl paratoluidine, 1,2,3,4
-Tetrahydroquinone and the like are preferable, and examples of the organic metal salt include copper chloride and copper octylate. Further, if necessary, a polymerization inhibitor such as benzoquinone, hydroquinone, hydroquinone monomethyl ether, phenol, ethylenediaminetetraacetic acid, (EDTA) and a sodium salt thereof may be used as a promoter or a stabilizer such as a secondary or tertiary amine. Chelating compounds such as oxalic acid, acetylacetone and o-aminophenols may be added.

When the flange material is an inert material such as plastic, or when the clearance is large and anaerobic hardening is difficult due to oxygen inhibition, the decomposition of organic peroxide is promoted on the flange surface to be joined in advance. By applying a curing accelerating primer containing a reducing agent that generates radicals, curing can be performed in a short time.

Examples of the curing accelerator containing a reducing agent which accelerates decomposition of an organic peroxide to generate a radical include a condensate of an aldehyde compound and a primary or secondary amine and / or an oxidizable transition metal. Contains compound. Specific examples of the condensation reaction product include, for example, butyraldehyde-butylamine condensate, butyraldehyde-aniline condensate, and acrolein-aniline condensate.

Examples of the oxidizable transition metal-containing compound include:
Among the organic compounds containing transition metals selected from the group of iron, cobalt, nickel and manganese, particularly useful are metal chelates or complex salts. Specifically, in addition to pentadione iron, pentadione cobalt, pentadione copper, propylene diamine copper, ethylene diamine copper, etc.,
Iron naphthate, nickel naphthate, cobalt naphthate, copper naphthate, copper octate, iron hexoate, iron propionate, vanadium acetylacetone and the like. In addition, substituted thioureas such as ethylene thiourea and benzothiazole can be used. In order to form a primer, the above-mentioned reducing compound is dissolved in an organic solvent such as toluene, acetone, methyl ethyl ketone, ethyl acetate or alcohol in the range of 0.05 to 10% by weight.

[0030] In addition, the sealant composition of the present invention may be provided with various fillers such as fumed silica for adjusting viscosity, plasticizers, and adhesion imparting properties such as silane compounds and phosphate esters, if necessary. Agents, various known acrylic acid ester monomers such as isobornyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, or the like to adjust rubber strength such as hardness and elongation; or A methacrylate monomer or the like may be blended.

[0031]

The anaerobic curable composition according to the present invention has flexibility even when subjected to heat history because core-shell fine particles are added as a functional filler to a combination of a urethane (meth) acrylate prepolymer and a radical polymerizable monomer. It is not extremely reduced and can be easily dispersed in the composition. Further, since the core-shell fine particles have an oil-absorbing property, the adhesive force does not decrease even on the surface where oil or the like is attached. Since the core-shell fine particles have a small particle size, the uncured anaerobic curable composition is easily dispersed in oil.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION

EXAMPLES The present invention will be described in detail with reference to formulation examples in order to explain the present invention more clearly. However, this embodiment does not limit the scope of the claims.

Production of sealant compositions 1 to 6 Urethane (meth) acrylate prepolymer UN-1101T (manufactured by Negami Kogyo Co., Ltd.) having a polyether in the main chain as a urethane (meth) acrylate prepolymer, and having a polyester in the main chain Urethane (meth) acrylate prepolymer UN-2500 (manufactured by Negami Industry Co., Ltd.) epoxy acrylate SP-1507 (manufactured by Showa Polymer), phenoxyethyl acrylate as a radical polymerizable monomer, cumene hydroperoxide as an organic peroxide, and further as a stabilizer Ethylenediaminetetraacetic acid (EDT
A), butylhydroxytoluene (BHT), saccharin, benzothiazole, n-dodecylmercaptan as an accelerator, Darocure 1173 (manufactured by Ciba-Geigy),
Silica as a filler, core-shell fine particles comprising a core of a rubber-like polymer and a shell of a glass-like polymer, F-
351 (manufactured by Nippon Zeon Co., Ltd.), XER-91 (manufactured by Nippon Synthetic Rubber Co., Ltd.), and Staphyloid IM-101 (manufactured by Takeda Pharmaceutical Co., Ltd.) were blended with Compositions 1 to 6 in a weight ratio as shown in Table 1.

Preparation of Comparative Sealant Compositions 7 to 12 Core-shell fine particles composed of a rubbery polymer core and a glassy polymer shell of Examples 1 to 6 were not added, and instead of these, ethylene acrylic rubber fine particles, liquid Compositions 7 to 12 were blended with butadiene-acrylonitrile, bis-2-ethylhexyl phthalate (DOP) as a plasticizer, and ethylene glycol at a weight ratio as shown in Table 2.

Examples 1-6, Comparative Examples 1-6: Thermal Degradation Test Darocur 11 as an ultraviolet curing catalyst was added to Compositions 1-12.
A sheet having a thickness of about 2 mm was prepared by irradiating ultraviolet light to which 73 was added, and a test piece of No. 2 dumbbell was prepared. This sample was placed in a circulating hot air dryer at 120 ° C and 150 ° C for 24 hours.
After curing for 0 hours, the elongation was measured. Table 3 shows the results.

Examples 7 to 12, Comparative Examples 7 to 12: Oil Surface Adhesion Test The oil surface shear adhesion of the compositions 1 to 12 was measured. The test piece was an aluminum plate (A2
024P), (size 1.6 x 25 x 100 mm). The bonding surface was polished with sandpaper # 240 and washed with toluene. About 0.5 mg / cm ² of auto transmission fluid was attached to one of the test pieces. Composition 1
Twelve anaerobic curable compositions were applied so as to protrude when the test pieces were overlapped on the other test piece, and the test pieces were overlapped by 10 mm. Using two washing scissors, they were sandwiched from both sides so as to press the overlapping surface. The tensile speed in the measurement of the shear adhesive strength was 10 mm / min. The curing time was 72 hours at 25 ° C. Table 4 shows the results.

Examples 13-18, Comparative Examples 13-18: Oil dispersibility test In a 500 ml glass beaker, 200 ml of auto transmission fluid was placed, and 0.2 g of compositions 1 to 12 were added. Thereafter, the mixture was stirred with a handy type stirrer for 3 hours (rotation speed: 500 rpm, stirring blade: propeller type, diameter 50 mm). Then, filter paper (500 mesh)
, And the residue was visually confirmed. ○, no residue
The presence of a residue was evaluated as x. Table 4 shows the results.

[0038]

The anaerobic curable sealant composition of the present invention is as flexible as the silicone composition, and maintains the flexibility and sealability that can cope with the vibration and stress of the seal portion such as between the flanges. Excellent repulsion only. Therefore, the followability of the sealant layer is high. Furthermore, even when used in a high-temperature atmosphere, excellent sealing properties can be maintained without lowering of flexibility.

The core-shell fine particles used in the present invention can be easily dispersed in a composition system as a functional filler,
The manufacturing process is easy and the manufacturing cost can be reduced.

Further, the anaerobic curable sealant composition of the present invention has an oil-absorbing effect, and has improved oil-surface adhesive strength as compared with the conventional anaerobic curable composition imparting flexibility. In other words, engine oil, lubricating oil such as auto transmission fluid, mold release agent at the time of molding, even if oil such as polishing oil on the flange surface adheres to the surface to be sealed, there is no need to degrease and wash with a solvent or cleaning agent. The manufacturing process can be simplified.

The uncured anaerobic curable composition to which the acrylic core-shell fine particles of the present invention are added is dispersed without agglomeration in oil. Therefore, when the seal for the flange surface of an engine such as an automobile or a transmission is used, the sealant composition protruding from the flange surface is uniformly dispersed without adversely affecting various oils.

Claims (1)

[Claims] 1. An anaerobic curable sealant comprising a urethane (meth) acrylate prepolymer, a radical polymerizable monomer and an organic peroxide, further comprising core-shell fine particles comprising a rubber-like polymer core and a glass-like polymer shell. An anaerobic curable sealant composition comprising: